PHOTO-ASSISTED FAST CHARGING OF LITHIUM MANGANESE OXIDE SPINEL (LiMn2O4) IN LITHIUM-ION BATTERIES

ABSTRACT

A process for charging a discharged electrochemical cell includes applying a voltage bias to the discharged electrochemical cell; and illuminating the cathode with a light source.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/651,806, filed on Jul. 17, 2017, which claims the benefit of priorityto U.S. Provisional Patent Application No. 62/364,071 filed Jul. 19,2016, all of which are hereby incorporated by reference, in theirentirety for any and all purposes.

GOVERNMENT RIGHTS

The United States Government has rights in this invention pursuant toContract No. DE-AC02-06CH11357 between the U.S. Department of Energy andUChicago Argonne, LLC, representing Argonne National Laboratory.

FIELD

The present technology is generally related to rechargeableelectrochemical cells, and more specifically is related to the use ofwhite light shown onto an electrode during the recharge cycle.

BACKGROUND

Lithium-ion batteries are typically slow-charged in order to promotelonger battery cycle life and obtain the full capacity (stored energy)of the battery. Depending on the chemistry, active particle physicalmorphologies, and low electrode loading, fast charging is feasible.

However, fast direct current (constant i) charging leads to unavoidabletemperature increases internal to the battery from resistive heating(e.g. i²R heating). Inductive (wireless) charging also intrinsicallyheats the battery. These deleterious conditions may cause degradation inthe battery. Lowering the time that takes to charge the battery wouldhelp make the overall device more efficient, usable and effective forthe application.

SUMMARY

In one aspect, an electrochemical cell is provided, the cell including acathode, an anode, a non-aqueous electrolyte, and a cathode illuminationsource configured to direct a light source at the cathode during acharging cycle. In some embodiments, the light source is a broadbandwhite or various monochromatic light source. In any of the aboveembodiments, the light source is a light emitting diode, a xenon lamp, alaser, or optical fiber. In any of the above embodiments, theillumination source may be a window in a housing for the electrochemicalcell, a fiber optic, or a light emitting diode. In some embodiments,both the illumination source and the light source are a light emittingdiode. In any of the above embodiments, the illumination source mayfurther include an infrared filter. In any of the above embodiments, theelectrochemical cell may be a lithium ion battery, a sodium ion battery,a magnesium ion battery, or a sulfur battery.

In another aspect, a process is provided for charging a dischargedelectrochemical cell, the process including: applying a voltage bias tothe discharged electrochemical cell; and illuminating the cathode with alight source; wherein: the discharged electrochemical cell includes acathode, an anode, a non-aqueous electrolyte, and an illuminationsource. In such an embodiment, the light source may be a broadband whitelight source. In any such embodiments, the light source may be a lightemitting diode, a xenon lamp, a laser, or optical fiber. In any of theabove embodiments, the illumination source may alternatively, or incombination, be a window in a housing for the electrochemical cell, afiber optic, or a light emitting diode. In any of the above embodiments,the illumination source may further include an infrared filter. In anyof the above embodiments, the electrochemical cell may be a lithium ionbattery, a sodium ion battery, a magnesium ion battery, or a sulfurbattery.

In another aspect, a method is provided for generating Mn⁴⁺ in anelectrode of an electrochemical cell, the method comprising applying acharging current to the electrochemical cell, and simultaneouslyilluminating the electrode with visible light. In such embodiments, thevisible light may be a broadband white light or a monochromatic light.In any such embodiments, the electrochemical cell may be a lithium ionbattery, a sodium ion battery, a magnesium ion battery, or a sulfurbattery. In such embodiments, the electrode may be a cathode asdescribed herein and containing a cathode active material as described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a modified coin cell amenable to lightimpingement through opening at sealed quartz window, according to oneembodiment.

FIG. 2A illustrates voltage profile of modified coin cell with hole, andFIG. 2B shows a voltage profile of a typical closed cell, according tothe examples.

FIGS. 3A and 3B are electrochemical impedance spectra of the open cellin as a Bode plot (3A) shown for dark (indicated by circle) and light(indicated by square) and a Nyquist plot (3B), both shown for dark(shown in open circle) and light (filled square) experiments. The opencell voltage was cell 3.59 V with 5 m V input AC signal amplitudebetween 10 kHz to 10 mHz. The open square curve in the Bode plot clearlyshows lower impedance versus open circle curve. The high frequencyintercept is nearly the same (Bode), indicating no change to the bulkelectrolyte cell resistance with light on.

FIG. 4 illustrates chronoamperometry measurements with the currentresponse being measured by applying a constant voltage of 4.07 V for 30min, and where the integrated area under the curve for ‘dark’ experimentis 0.32 C and for ‘light’ is 2.28 C, and the dark state is indicated byopen circles and light on state is indicated by filled squares).

FIG. 5 shows the discharge voltage profile, where after the ‘light’experiment, a higher energy density was sustained (indicated in red) ascompared to the ‘dark’ state condition shown in blue curve. The specificcapacity is 29 mAh/g (post-light) versus 3 mAh/g (no light), an increaseof over a magnitude in stored charge. A value of 0.5 mA constant currentwas applied for the measurements. (Dark is indicated by a solid line,light is indicated in a dash line).

FIGS. 6A, 6B, and 6C are (A) AC impedance spectra with light on versusdark state in coin cell (Voc=3.5 V) as above in FIG. 1 . (B)Chronoamperometry curves for light-on versus dark state during constantvoltage hold charging at 4.07 V (vs. Li metal counter electrode) forapproximately 23 minutes. (For both (A) and (B), the dark state isindicated by open circles and light on state is indicated by filledsquares) (C) Unlighted constant discharge curves (voltage profiles) forcells post-‘light-on’ versus ‘dark’ state cells, according to oneembodiment (Dark is indicated by a solid line, light is indicated in adash line).

FIGS. 7A and 7B illustrate a continuous wave (CW) X-band EPR spectra ofcharged LiMn₂O₄ battery (A) before illumination and (B) duringillumination (red spectrum) with white light from a Xenon lamp, T=10 K.,and (C) time dependence of the EPR signal at 210 mT before, during, andafter illumination. Note that the CW EPR results in a derivative-typelineshape, according to one embodiment.

FIG. 8 illustrates continuous wave (CW) X-band EPR spectra of LiMn₂O₄spinel before illumination (“dark”) and during illumination (“light”)with a white light at T=10 K, according to the examples.

FIG. 9A illustrates the electrochemical performance of a light acceptinglithium ion battery cell during charging, and FIG. 9B illustrates thesame during discharge, for both light-on and light-off states, accordingto the examples.

FIG. 10 illustrates the effect of temperature on the charge anddischarge capacities, according to the examples.

DETAILED DESCRIPTION

Various embodiments are described hereinafter. It should be noted thatthe specific embodiments are not intended as an exhaustive descriptionor as a limitation to the broader aspects discussed herein. One aspectdescribed in conjunction with a particular embodiment is not necessarilylimited to that embodiment and can be practiced with any otherembodiment(s).

As used herein, “about” will be understood by persons of ordinary skillin the art and will vary to some extent depending upon the context inwhich it is used. If there are uses of the term which are not clear topersons of ordinary skill in the art, given the context in which it isused, “about” will mean up to plus or minus 10% of the particular term.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the elements (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein are merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range, unless otherwise indicated herein, andeach separate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the embodiments and does not pose alimitation on the scope of the claims unless otherwise stated. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential.

Disclosed herein are lithium ion batteries and processes that allow forfast direct current charging (as well as recharging) without the severeeffects produced through resistive heating. This is accomplished byirradiating the cathode electrode, during charging, with bright whitelight to lower activation barriers to charge transport and ionicdiffusion. It has been observed that when irradiated with bright whitelight the electrode charges faster without, or with only minimal,deleterious side effects in the battery, or destruction of the inherentability of the cathode to normally operate. Monitor the temperature ofthe cell during “light-on” show no, or only minimal, cell heating duringcharging.

Without being bound by theory, it is believed that irradiation of aLi-ion battery cathode electrode material surface with a broadband whitelight generates photo-induced energy transfer process wherein the lightenergy lowers charge-transfer resistance, along with other kinetic andthermodynamic barriers. The result is a battery that exhibits fasterelectrochemical reactions, the effect of which is faster charging incomparison to a battery that is no irradiated with white light (i.e. a“dark state battery”). The dark state battery is the common type ofbattery in use in today's market. However, after light activation andimpingement, the subsequent discharge results in greater usable capacityand voltage, which in turn leads to higher energy density. Asemi-conducting to metallic-like electronic state change is enhanced inthe electrode material observed as a photo-current, wherein electronconduction is increased within the band structure of the electrodematerial. This light-assisted reaction lowers transport barrier tocation diffusion through the electrode/electrolyte interface and thebulk crystal charge-carrying ion motion. Such a process can be used tofast charge cells and batteries such as lithium-ion batteries, as wellas other non-aqueous batteries that feature a cathode electrolyteinterphases (CEIs) and intrinsically active phases with low electronicconductivity (i.e. insulators).

As further explanation of the theory as to how the charging rate isincreased under light illumination, the example of a cathode thatincludes manganese is described. For example, where the cathode of alithium ion battery includes LiMn₂O₄ (LMO) spinel oxide, it is has beenshown that exposure of the cathode to broadband white light underpotential bias increases the electrode kinetics and the associatedelectrochemical charging rates.

Light (illumination) assists in the fast charging of LMO-based cells.Without being bound by theory, it is believed that photoexcitationprimarily injects ligand holes into the oxygen 2p band and an electronis promoted to the manganese 3d conduction band. The hole formallyoxidizes O²⁻ to O⁻, while the electron reduces a Mn species; in LMO thiswill be either Mn⁴⁺ to Mn³⁺ or Mn³⁺ to Mn²⁺. Under a potential bias theelectron percolates through the structure via intervalence chargetransfer/polaron hopping towards the current collector, where theelectron passes into the external circuit and Mn is reoxidized. Sincethe Mn 3d valence bands are hybridized with O 2p bands, it isenergetically favorable for the hole in the oxide band to be eliminatedfrom the structure by moving to a formally Mn 3d band. In chemicalterms, in a Mn³⁺—O⁻(hole)-Mn^(3/4+) bridge charge transfer occurs wherean electron is transferred from Mn³⁺ to the bridging oxygen, therebyoxidizing Mn³⁺ to Mn⁴⁺ and a Li⁺ is ejected from the structure.Therefore, light incident on the LMO cathode during device charginginitiates a lithium deinsertion process associated with anion basedredox activity that acts in concert with the 3d metal cation based redoxpresent in conventional batteries (i.e., in the ‘light-off’ state). Inthe proposed mechanism the net change in Mn oxidation state prior toelectron and Li⁺ removal can be summarized in equations 1(A) and (B).

In one aspect, an electrochemical cell includes a cathode, an anode, anon-aqueous electrolyte, and a cathode illumination source that isconfigured to direct a light source to the cathode during a chargingcycle. The electrochemical cell may be a rechargeable electrochemicalcell. In such cells, the light source may be a broadband white light ora monochromatic light source. For example, the light source may be, butnot limited to, the sun, a light emitting diode, a xenon lamp, a laseror optical fiber light with the appropriate energy for band gapexcitement. In some embodiments, the illumination source may include aninfrared filter to prevent, or minimize to the extent possible, infraredheating of the cell.

(A) Mn³⁺+Mn⁴⁺→Mn⁴⁺+Mn³⁺

(B) 2Mn³⁺→Mn⁴⁺+Mn²⁺  [1]

In both cases electron transfer from Mn³⁺ to a neighboring Mn^(3+/4+)generates a Mn⁴⁺, however in (A) the electron reduces a Mn⁴⁺ to Mn³⁺while in (B) a Mn³⁺ is reduced to Mn²⁺, i.e., disproportionation.

The illumination source may be any source that may provide light to thecathode of the electrochemical cell during charging. For example, theillumination source is used in conjunction with an optical windowlocated in a housing for the electrochemical cell, such that an externallight source may be used to direct light through the window to thecathode. The window may be a plastic, quartz, glass, BaF₂, or othermaterial that will allow for the passage of the light with minimalabsorption in the wavelength of interest.

The illumination source may also be a fiber optic. That is, theillumination source may be fiber optic that can deliver light to theelectrochemical cell. The fiber optic may be used to direct lightthrough a window, or directly into the cell through a port in thehousing of the electrochemical cell. The fiber optic carries light fromthe light source, which may be external to the electrochemical cell.

The light source may be a light emitting diode (LED) source that can belocated directly in the cell with the cathode material such that duringa charging cycle the LED may be turned on to illuminate the cathode. Insuch a situation, the LED may be an external light sources that is usedto illuminate the cathode during charging. However, the LED in certainembodiments may be both the illumination source and the light source,when the LED is proximally located to the cathode within the housing ofthe electrochemical cell, such that during charging the LED may beturned on an deliver light directly to the cathode.

As noted above, the electrochemical cell contains a non-aqueouselectrolyte and is thus a non-aqueous electrochemical cell. This thusmay include other non-aqueous cells, but is not limited to a lithium ionbattery; thus a sodium ion battery, a magnesium ion battery, lithium airor a lithium sulfur battery are envisioned whereby these chemistriesinteract positively with light to allow faster recharging.

The cathode, as noted above may have a wide bandgap, be a ceramic or asemiconductor. According to some embodiments, it is believed that a thereason that illumination of the cathode is believed to work is due tothe light providing the requiring energy to overcome the band gap in thecathode active material. Accordingly, in some embodiments, the cathodeactive materials have band gaps ranging from approximately 1.3 eV to 4eV. Moreover, the light energy is used to assist and overcome theactivation energy required for carrier mobility including enhancingconduction through polaronic mechanisms.

Illustrative cathode active materials may include, but are not limitedto, a spinel, a olivine, a carbon-coated olivine, LiFePO₄, LiCoO₂,LiNiO₂, LiNi_(1−x)Co_(y)M⁴ _(z)O₂, LiMn_(0.5)Ni_(0.5)O₂,LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄, LiFeO₂, LiM⁴ _(0.5)Mn_(1.5)O₄,Li_(1+x)Ni_(α)Mn_(β)Co_(γ)M⁵ _(δ′)O_(2−z″)F_(z″), or VO₂. In the cathodeactive materials, M⁴ is Al, Mg, Ti, B, Ga, Si, Mn, or Co; M⁵ is Mg, Zn,Al, Ga, B, Zr, or Ti; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu, or Zn; B¹is Ti, V, Cr, Fe, or Zr; 0≤x≤0.3; 0≤y≤0.5; 0≤z≤0.5; 0≤x″≤0.4; 0≤α≤1;0≤β≤1; 0≤γ≤1; 0≤δ′≤0.4; 0≤z″≤0.4; and 0≤n′≤3; with the proviso that atleast one of α, β and γ is greater than 0. In some embodiments, thecathode includes LiFePO₄, LiCoO₂, LiNiO₂, LiNi_(1−x)CO_(y)M⁴ _(z)O₂,LiMn_(0.5)Ni_(0.5)O₂, LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄,LiCr_(0.5)Mn_(1.5)O₄, LiCrMnO₄, LiFe_(0.5)Mn_(1.5)O₄,LiCo_(0.5)Mn_(1.5)O₄, LiCoMnO₄, LiCoMnO₄, LiNi_(0.5)Mn_(1.5)O₄, LiNiPO₄,LiCoPO₄, LiMnPO₄, LiCoPO₄F, Li₂MnO₃, Li₅FeO₄, and Li_(x′)(Met)O₂,wherein Met is a transition metal and 1<x′≤2. In some embodiments, Metis Ni, Co, Mn, or a mixture of any two or more thereof. In someembodiments, Met is a mixture of Ni, Co, and Mn. In some embodiments,the cathode active material may include LiFePO₄, LiCoO₂, LiNiO₂,LiNi_(1−x)CO_(y)M⁴ _(z)O₂, LiMn_(0.5)Ni_(0.5)O₂,LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄, LiCr_(0.5)Mn_(1.5)O₄, LiCrMnO₄,LiFe_(0.5)Mn_(1.5)O₄, LiCo_(0.5)Mn_(1.5)O₄, LiCoMnO₄, LiCoMnO₄,LiNi_(0.5)Mn_(1.5)O₄, LiNiPO₄, LiCoPO₄, LiMnPO₄, LiCoPO₄F, Li₂MnO₃,Li₅FeO₄, or Li_(x′)(Met)O₂, where Met is a transition metal and 1<x′≤2.Other materials may include metallic or semiconducting particles, orplasmonic particles that create nascent electric fields when irradiatedby white light.

In some embodiments, the cathode may include a cathode active materialthat includes manganese. In such embodiments, the cathode activematerial may include, but is not limited to LiMn_(0.5)Ni_(0.5)O₂,LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄, LiM⁴ _(0.5)Mn_(1.5)O₄,Li_(1+x″)Ni_(α)Mn_(β)Co_(γ)M⁵ _(δ′)O_(2−z″)F_(z″), LiMn_(0.5)Ni_(0.5)O₂,LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄, LiCr_(0.5)Mn_(1.5)O₄, LiCrMnO₄,LiFe_(0.5)Mn_(1.5)O₄, LiCo_(0.5)Mn_(1.5)O₄, LiCoMnO₄, LiCoMnO₄,LiNi_(0.5)Mn_(1.5)O₄, LiMnPO₄, or Li₂MnO₃, where M⁴ is Al, Mg, Ti, B,Ga, Si, Mn, or Co; M⁵ is Mg, Zn, Al, Ga, B, Zr, or Ti; 0≤x″≤0.4; 0≤α≤1;0<β≤1; 0≤γ≤1; 0≤δ′≤0.4; 0≤z″≤0.4; and 0≤n′≤3.

Additionally, the anode may also include metallic anode active materialssuch as lithium, sodium, or magnesium; sulfur materials; or carbonmaterials including, but not limited to, synthetic graphite, naturalgraphite, amorphous carbon, hard carbon, soft carbon, acetylene black,mesocarbon microbeads (MCMB), carbon black, Ketjen black, mesoporouscarbon, porous carbon matrix, carbon nanotube, carbon nanofiber, orgraphene. In any of the above embodiments, the anode may include agraphite material, alloys, intermetallics, silicon, silicon oxides, TiO₂and Li₄Ti₅O₁₂, and composites thereof.

The cathodes and/or anodes of the lithium ion cells also include acurrent collector. Current collectors for either the anode or thecathode may include those of copper, stainless steel, titanium,tantalum, platinum, gold, aluminum, nickel, cobalt nickel alloy, highlyalloyed ferritic stainless steel containing molybdenum and chromium; ornickel-, chromium-, or molybdenum-containing alloys.

The anodes and cathodes may include a binder that holds the activematerial and other materials in the electrode to the current collector.Illustrative binders include, but are not limited to, polyvinylidenedifluoride (PVDF), polyvinyl alcohol (PVA), polyethylene, polystyrene,polyethylene oxide, polytetrafluoroethylene (Teflon), polyacrylonitrile,polyimide, styrene butadiene rubber (SBR), carboxy methyl cellulose(CMC), alginate, gelatine, a copolymer of any two or more such polymers,or a blend of any two or more such polymers.

The electrochemical cells may also include a separator between thecathode and anode to prevent shorting of the cell. Suitable separatorsinclude those such as, but not limited to, a microporous polymer filmthat is nylon, cellulose, nitrocellulose, polysulfone,polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene,polybutene, or a blend or copolymer thereof. In some embodiments, theseparator is an electron beam treated micro-porous polyolefin separator.In some embodiments, the separator is a shut-down separator.Commercially available separators include those such as, but not limitedto, Celgard® 2025 and 3501, Tonen separators and ceramic-coatedseparators.

The non-aqueous electrolyte may include a non-aqueous solvent and asalt. Illustrative non-aqueous solvents include, but are not limited to,silanes, siloxanes, ethylene carbonate, dimethylcarbonate,diethylcarbonate, propylene carbonate, dioloxane, γ-butyrolactone,δ-butyrolactone, dimethyl ether, a silane, siloxane N-methyl acetamide,acetonitrile, an acetal, a ketal, esters, a carbonates, a sulfone, asulfite, sulfolane, an aliphatic ether, a cyclic ether, a glyme, apolyether, a phosphate ester, a siloxane, a N-alkylpyrrolidone, fluoroether and fluoro esters, fluoroethylene carbonate, or adiponitrile, or afluorinated solvent. Illustrative fluorinated solvents include thoserepresented by Formula I, II, III or IV:

R¹—O—R²  Formula I

R¹—C(O)O—R²  Formula II

R¹—OC(O)O—R²  Formula III

R¹—S(OO)—R²  Formula V

In Formulas I, II, III, IV, and V, R¹ and R² are individually a an alkylor C_(n)H_(x)F_(y) group; R³ and R⁵ are individually O or CR⁶R⁷; R⁴ is Oor C═O; each R⁶ and R⁷ is individually H, F or a C_(n)H_(x)F_(y) group;each x is individually from 0 to 2n; each y is individually from 1 to2n+1; and each n is individually an integer from 1 to 20. However, theformulae are also subject to the following provisos: at least one of R¹and R² is a C_(n)H_(x)F_(y) group; at least one R⁶ or R⁷ is other thanH, and R⁴ is not O when R³ or R⁵ is O. In some embodiments, R¹ and R²are individually CF₂CF₃; CF₂CHF₂; CF₂CH₂F; CF₂CH₃; CF₂CF₂CF₃;CF₂CF₂CHF₂; CF₂CF₂CH₂F; CF₂CF₂CH₃; CF₂CF₂CF₂CF₃; CF₂CF₂CF₂CHF₂;CF₂CF₂CF₂CH₂F; CF₂CF₂CF₂CH₃; CF₂CF₂CF₂CF₂CF₃; CF₂CF₂CF₂CF₂CHF₂;CF₂CF₂CF₂CF₂CH₂F; CF₂CF₂CF₂CF₂CH₃; or CF₂CF₂OCF₃. In some embodiments,the fluorinated solvent includes CHF₂CF₂OCF₂CF₂CF₂H;

As noted, the non-aqueous electrolyte may include a non-aqueous solventand a salt. The salt may be a salt as known for use in a lithium ion,sodium ion, magnesium ion, or other battery. For example, the salt maybe a lithium salt. Suitable lithium salts include, but are not limitedto, LiBr, LiI, LiSCN, LiBF₄, LiAlF₄, LiPF₆, LiAsF₆, LiClO₄, Li₂SO₄,LiB(Ph)₄, LiAlO₂, Li[N(FSO₂)₂], Li[SO₃CH₃], Li[BF₃(C₂F₅)],Li[PF₃(CF₂CF₃)₃], Li[B(C₂O₄)₂], Li[B(C₂O₄)F₂], Li[PF₄(C₂O₄)],Li[PF₂(C₂O₄)₂], Li[CF₃CO₂], Li[C₂F₅CO₂], Li[N(CF₃SO₂)₂], Li[C(SO₂CF₃)₃],Li[N(C₂F₅SO₂)₂], Li[CF₃SO₃], Li₂B₁₂X_(12−n)H_(n), Li₂B₁₀X_(10−n′)H_(n′),Li₂S_(x″), (LiS_(x″)R¹)_(y), (LiSe_(x″)R¹)_(y), and lithium alkylfluorophosphates; where X is a halogen, n is an integer from 0 to 12, n′is an integer from 0 to 10, x″ is an integer from 1 to 20, y is aninteger from 1 to 3, and R¹ is H, alkyl, alkenyl, aryl, ether, F, CF₃,COCF₃, SO₂CF₃, or SO₂F. In any of the above embodiments, the saltincludes Li[B(C₂O₄)₂], Li[B(C₂O₄)F₂], LiClO₄, LiBF₄, LiAsF₆, LiPF₆,LiCF₃SO₃, Li[N(CF₃SO₂)₂], Li[C(CF₃SO₂)₃], Li[N(SO₂C₂F₅)₂], or a lithiumalkyl fluorophosphate.

In another aspect, a process is providing for charging a dischargedelectrochemical cell, the electrochemical cell being any of those asdescribed above in any embodiment. The process includes applying avoltage bias to the discharged electrochemical cell; and illuminatingthe cathode with a light source, wherein the discharged electrochemicalcell comprises a cathode, an anode, and a non-aqueous electrolyte. Theillumination source may be a window in a housing for the electrochemicalcell, a fiber optic, or a light emitting diode.

In the process, the illumination source may a light source. The lightsource may, in some embodiments be a broadband white light source. Forexample, the illumination source may be the sun, a light emitting diodesource, a xenon source, or a laser with the appropriate energy forelectron excitement of the active battery material. The illuminationsource may further include an infrared or to prevent, or at leastminimize, heating of the electrochemical cell and/or cathode. In theprocess, the electrochemical cell may be a lithium ion battery, a sodiumion battery, a magnesium ion battery, or a sulfur battery. The use ofthe illumination source for the cathode may result in a reduction incharging time. In some embodiments, the reduction is a 10% reduction incharging time compared to a cell without the illumination source. Thisincludes reductions of 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%,65%, 70%, 75%, or 80%, or more. In some embodiments, the reduction incharging time is a 25% reduction in charging time compared to a cellwithout the illumination source. In some embodiments, the reduction incharging time is a 50% reduction in charging time compared to a cellwithout the illumination source. In some embodiments, the reduction incharging time is a 75% reduction in charging time compared to a cellwithout the illumination source. In some embodiments, the reduction incharging time is a 25-75% reduction in charging time compared to a cellwithout the illumination source.

Also disclosed herein are light stations that may be used in conjunctionwith direct current charging stations as necessary for recharge ofelectric vehicles or plug-in electric vehicles. For example, existinggas, rest area, or other roadway stations will be able to use existingelectrical infrastructure at their locations to service the lightstations to provide power to the illumination source in order tophoto-assist charging processes, where the batteries are those used inhybrid or electric vehicles. The light stations will look like gaspumps, but, instead will house lamps and will have their own island toeasily allow servicing electric cars with the proper light harvestingtechnology.

The present invention, thus generally described, will be understood morereadily by reference to the following examples, which are provided byway of illustration and are not intended to be limiting of the presentinvention.

EXAMPLES

Generally. During charge, LiMn₂O₄ is bulk oxidized, lithium leaves thematerial, and lithium cations are reduced with lithium metal depositionat the opposite anode (in this case lithium metal); the electrons travelin the external circuit with high potential ˜4.0 V. Typically, acomposite electrode consisting of a polytetrafluoroethylene binder,(e.g. —(CF₂)_(n)—), carbon particles as conductive diluent (e.g.acetylene carbon black), and active oxide powder in weight ratio of20:5:75% is used and the assemblage is optimized for this process. Thebinder keeps particles in laminate form, the carbon, to provideconductivity network amongst the particles, and active material oxide,to support the electrochemical reaction and act as lithium cation host.For LiMn₂O₄, the oxidation state changes from Mn(III) to Mn(IV) withinthe bulk depending on the state of charge of the battery and the amountof Li in the material. During charge, high oxygen activity at thesurface initiates and increases with state-of-charge. Thus, locally, theconcentration of nascent Mn³⁺ at the LiMn₂O₄ electrode surface isnominally increased compared to the bulk.

The bandgap of LiMn₂O₄ is about 2-3 eV, thus it exists as a poorsemiconductor, but one that may form electron-hole pairs if excitationenergy is high enough to populate the conduction band with electrons.Where energy (E), E=hf=hc/λ. Here h=6.626*10⁻³⁴ Js is a universalconstant called Planck's constant, and a photon with a wavelength of 450nm possesses an energy of 2.76 eV and therefore is capable of promotingelectrons into a conduction band in the material, and formation of holes(h⁺) in the valence band creating a charge-separated state.

Window cell formation. A modified or ‘open’ light-accepting coin cellbattery with a punched hole in the exterior was formed. Over the hole atransparent quartz window (superior transmittance in the UV and Visiblespectrum regions) was sealed in place, allowing light to enter the cellthrough the window (see FIG. 1 ). The electrode is pressed onto an Almesh screen and is built into the cell with a metallic lithium counterelectrode and a glass fiber separator soaked with the lithiumhexafluorophosphate salt containing aprotic ester-carbonate basedsolvent. The cell is crimped and thus hermetically sealed to ambientatmosphere. This cathode/Al-mesh design allows for both an even currentdistribution across the electrode sheet, but also can be mounted at anyangle for light impingement during cell cycling (charging anddischarging the energy). The spectral output of the xenon lamp broadbandlight spans from about 200 nm to about 1100 nm, but an IR bandpassfilter is used in conjunction to minimize any heating of the cell fromthe light. There was a temperature increase of approximately 7° C. whenelectrochemical measurements were carried out under approximately onesun condition (100 mW/cm²), as measured with an IR thermometer pointedat the cell opening. Estimated energy flux ranging from 100 to 400mW/cm² is used for experiments.

Example 1. A modified 2032 coin cell is constructed having a lithiumanode, a glass fiber separator soaked in electrolyte, and a compositecathode of polytetrafluoroethylene, acetylene black carbon (TAB), andlithium manganese oxide spinel (LiMn₂O₄) as an active phase. The weightratios of TAB:LiMn₂O₄ are 25 wt %:75 wt %. The cathode is afree-standing film rolled out, and pressed into an Al mesh grid in orderto make electrical contact to the metal cell top, but also allow lightto interact with the cathode. To allow the white light to impinge on thecathode, a 8 mm diameter hole is punched out of the cell bottom, and aquartz (SiO₂) window is affixed to the bottom and sealed to blockambient air and leave it hermetically closed.

As illustrated in FIG. 1 , the cell is open whereby white light can beshone onto the cathode material during charging. The spectral output ofthe white light is from about 200 nm to about 1100 nm, and an infraredbandpass filter is used in conjunction with the window to block heatingof the cell from infrared light. The estimated energy flux for theexperiments can be varied from 100 to 400 mW/cm² at the sample. Theinput power of the light may be adjusted based on the desired flux.

To show electrochemical viability, the open cell battery was cycled inthe “dark” state, as demonstrated and shown in FIG. 2A. The cell wascycled at a current density of 0.5 mA, between 3.2 V and 4.4 V at ratesranging from 2 C to C/10 (calculated based upon a theoretical capacityof 148 mAhg⁻¹ for LiMn₂O₄). Yielding a reversible specific capacity of130 mAhg⁻¹ demonstrates the expected operation of the cell, and the nearcomplete utilization of the cathode (88% of theoretical). The voltageprofiles are also ideal, and nearly match the marked voltage profiles ofFIG. 2B, which is the response of a Li/LiMn₂O₄ closed coin cell withconventional laminate. The electrochemical impedance Nyquist and Bodeplots taken at cell voltage 3.59 V with a 5 mV AC signal amplitudebetween 10,000 Hz to 0.01 Hz is given in FIGS. 3A and B. The impedanceof the cathode material in the light state is significantly lower thanthe ‘dark’ state. This indicates a lowering of all uphill barriers suchas the electrode interfacial impedance, the charge transfer resistanceand the bulk Li cation diffusion. The inductive loop indicated in thefilled square curve is presumably due to non-equilibrium conditions inthe cell during ‘light-on’ state. Nonetheless, indications are that thelower overall impedance should bode well for better (faster) charging.

FIG. 4 encompasses an experiment whereby a constant voltage of 4 V isdelivered to the cell, and the current is measured. Certainly theexpectation of an exponential decay of current (i) in time should occurand indeed is observed. In contrast, the light irradiated cell shows acompletely different current i vs. time trace. First, the magnitude ofcurrent produced at the outset is about times higher than the ‘dark’state, and then after a slight downward, then upward peak like behavior,the current continues to be maintained for the duration of the 30 minuteexperiment.

FIG. 5 shows the voltages profiles for the follow-up discharge in the‘dark’ state. The sustained voltage at approximately 3.8 V (dash linecurve) indicates a higher energy density versus the ‘dark’ statecondition (solid line curve; no capacity/low voltage). Specific capacityis 17 mAh/g (light) versus 3 mAh/g, an increase of over a magnitude ofstored charge.

Example 2. Similar to Example 1, another cell was prepared. Duringtesting, after a one charge-discharge ‘dark’ cycle, the electrochemicalimpedance Nyquist plots were taken at 3.59 V open circuit potential witha 5 mV AC signal amplitude between 10 kHz to 0.01 Hz as shown in FIGS.6A, 6B, and 6C. The impedance of the cathode material in the light stateis significantly lower than the ‘dark’ state. This indicates a loweringof all uphill barriers such as the electrode interfacial impedance, thecharge transfer resistance and the bulk Li cation diffusion. All ofthese processes are kinetically improved. A second set of control ACimpedance experiments were conducted under dark state with the cellimpedance analyzed at 37° C. and 50° C. Very little difference in theimpedance spectra was observed thus providing additional evidence thatheat does not have a large effect on the material response in thisconfiguration.

FIG. 6B encompasses a DC experiment whereby a constant voltage of 4.07 Vis delivered to the cell, and the current is measured. Beginning about2.7 mA and falling off to about 1.2 mA after about 23 minutes is thetrace output. The amount of capacity gleaned from the material throughintegrating the charge in time is 2.29 C, or 27 mAh/g (based on theoxide active weight; chemical state is LiMn₂O₄). Even after ˜23 minutesthe current is still relatively high and the reaction continues. Fromthe galvanostatic result in FIG. 6B, the amount of capacity expected at4.07 V should be approximately 60 mAh/g (C); clearly the ‘dark’ statecell does not reach 60 mAh/g. In contrast, the light irradiated cellshows a completely different current i vs. time trace. First, themagnitude of current produced at the outset is about 4 times higher thanthe ‘dark’ state, and then after an exponential decrease downward,followed by a slight S-shape, next a linear region occurs at 600 seconds(10 minutes) proceeding to near zero current after about 23 minutes(1400 seconds).

FIG. 6C shows the voltage profiles for the follow-up constant currentunlighted discharge. The sustained voltage at approximately 4.0 Vindicates a reversible electrochemical reaction and one that is higherenergy density for light-on versus the ‘dark’ state condition. Specificcapacity or charge stored per weight is 60 mAh/g (light-on) versus 27mAh/g (dark state), or an increase of about twice the stored charge.Moreover, the coulombic efficiency for both are near 100% indicating afully reversible electrochemical reaction.

The “dark” state electrode impedance spectrum is the circle curve, whilethe light-on impedance spectrum is in square. The impedance of thecathode material in the light state is significantly lower than the darkstate. This indicates a lowering of all uphill barriers such as theelectrode interfacial impedance, the charge transfer resistance and thebulk Li cation diffusion. All of these processes are kineticallyimproved. The inductive loop in the red curve is presumably due tonon-equilibrium conditions in the cell during “light-on” state.Nonetheless, indications are that the lower overall impedance shouldbode well for better (faster) charging.

Electron paramagnetic resonance (EPR) conducted at 10 Kelvin (to slowback electron transfer) in a light state versus a control dark stateindicates a photo-oxidation process occurs generating a higherpopulation of Mn⁴⁺ holes at the surface that drives thechemical-electrochemical coupled reactions. See FIGS. 7 and 8 .

FIGS. 7A and 7B show the low temperature continuous wave (CW) X-band EPRspectra of the charged LiMn₂O₄ battery (4.07 V) during illumination(FIG. 7 A). Note that the CW EPR method results in a derivative-typelineshape. Before illumination, in the center of the spectrum at 340 mT(corresponding to g equal to about 2) a narrow and intense signal isobserved which we attribute to defects in the carbon and binder part ofthe composite cathode. The six line signal with approximately 50 mTtotal width is typical for Mn²⁺ ions. Since Mn²⁺, even in smallconcentration, gives intense signals, the actual amount of Mn²⁺ in thebattery material may be relatively small. A broad signal with severalhundreds of mT, centered at g≈2 is observed, which is typical forparamagnetic Mn⁴⁺ ions interacting with many close-by paramagnetic ionslike other Mn⁴⁺ ions or Mn³⁺ in LiMn₂O₄ spinels. Trivalent Mn³⁺ ionsthemselves are not directly observable under the experimentalconditions. Upon illumination, a new additional broad signal with awidth of approximately 215 mT, less width than the broad ‘dark’ Mn⁴⁺signal, is generated. This type of signal is typical for Mn⁴⁺ in LiMn₂O₄spinel, but has different coordination and/or magnetic surrounding thanthe ‘dark’ Mn⁴⁺ signal.

FIG. 7B shows that this signal is created rapidly after illuminationstarts, reaches a plateau, and decays almost quantitatively, afterillumination is ceased. The generation of Mn⁴⁺ ions is in agreement withthe photochemically induced disproportionation reaction outlined ineq. 1. Control samples with the carbon, binder and electrolyte, neatLiMn₂O₄, the LiMn₂O₄ being combined with electrolyte but without carbonbinder were also measured. The carbon/binder with electrolyte gave onlya radical signal (g of about 2.0035, lw_(pp)=0.5 mT) before and duringthe illumination. Both neat LiMn₂O₄ and LiMn₂O₄ with electrolyte gavealso broad Mn⁴⁺ signals before illumination, and showed light-inducedkinetics of Mn⁴⁺ creation and decay after illumination ceased.Interestingly, the LiMn₂O₄ with electrolyte showed slower rise and decaytimes. It is believed that that may be attributed to the absence of thecarbon and binder which can act as an electron shuttle/buffer. Insummary, FIGS. 7A and 7B are representative of the fact that more Mn⁴⁺signal is produced with light on, meaning the reaction with light isoccurring and the material is responding to light, by being oxidized (orlight-charged).

Example 3. Similar to Examples 1 and 2, a further cell was prepared.Electrochemical performance of the cell (Li∥1.2 M LiPF₆; EC:EMC 3:7(w:w) ∥LMO; (EC=ethylene carbonate; EMC=ethyl methyl carbonate; LMO isLiMn₂O₄) was tested and is presented in FIGS. 9A and B. In FIG. 9A, thecharge (chronoamperometry at 4.07 V vs. Li^(+/o) for 5 minutes), and, inFIG. 9B, the discharge (galvanostatic discharge at C/10) were observed.The charge/discharge capacities in the ‘light off’ state yielded30.14/29.92 mAh g⁻¹ and 29.55/29.28 mAh g⁻¹ before and after the ‘lighton’ experiment, respectively. In the ‘light on’ state thecharge/discharge capacities were 41.60/40.87 mAh g⁻¹, representing acapacity increase of 1.38 times or an increase in the charging rate by afactor of 1.7 compared to the ‘light-off’ state.

Example 4. The electrochemical performance of a light accepting ‘open’lithium ion battery cell during charge (chronoamperometry at 4.07 V vs.Li^(+/o) for 5 minutes) with respect to temperature is illustrated byFIG. 10 . Li∥11.2 M LiPF₆; EC:EMC 3:7 (w:w)∥LMO (EC=ethylene carbonate;EMC=ethyl methyl carbonate). The temperature was controlled to within±0.2° C. using a Maccor heat/cool temperature chamber (MTC-010) and thecell was allowed to equilibrate at each temperature for 2 h beforetesting. The charge and discharge capacities, along with the cyclingefficiency and capacity increase compared to the 25° C. experiment, areshown in the table inset. In the elevated temperature experiments thecapacity increase ranged from 1.06-1.26, and the charging rate increasedby a factor of 1.09-1.45, compared to the 25° C. experiment.

Para. A. In one aspect, an electrochemical cell comprising a cathode, ananode, a non-aqueous electrolyte, and a cathode illumination sourceconfigured to direct a light source at the cathode during a chargingcycle.

Para. B. The electrochemical cell of Para. A, wherein the light sourceis a broadband white light source or a monochromatic light source.

Para. C. The electrochemical cell of Para. A or B, wherein the lightsource is a light emitting diode, a xenon lamp, a laser, or opticalfiber.

Para. D. The electrochemical cell of any one of Paras. A-C, wherein theillumination source is a window in a housing for the electrochemicalcell.

Para. E. The electrochemical cell of any one of Paras. A-D, wherein theillumination source is a fiber optic.

Para. F. The electrochemical cell of any one of Paras. A-E, wherein theillumination source and the light source are both a light emittingdiode.

Para. G. The electrochemical cell of any one of Paras. A-F, wherein theillumination source further comprises an infrared filter.

Para. H. The electrochemical cell of any one of Paras. A-G, wherein theelectrochemical cell is a lithium ion battery.

Para. I. The electrochemical cell of any one of Paras. A-H, wherein thecathode comprises a cathode active material comprising a spinel, aolivine, a carbon-coated olivine, LiFePO₄, LiCoO₂, LiNiO₂,LiNi_(1−x)Co_(y)M⁴ _(z)O₂, LiMn_(0.5)Ni_(0.5)O₂,LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄, LiFeO₂, LiM⁴ _(0.5)Mn_(1.5)O₄,Li_(1+x″)Ni_(α)Mn_(β)Co_(γ)M⁵ _(δ′)O_(2−z″)F_(z″), A_(n′)B¹ ₂(M²O₄)₃, orVO₂; wherein: M⁴ is Al, Mg, Ti, B, Ga, Si, Mn, or Co; M⁵ is Mg, Zn, Al,Ga, B, Zr, or Ti; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu, or Zn; B¹ isTi, V, Cr, Fe, or Zr; 0≤x≤0.3; 0≤y≤0.5; 0≤z≤0.5; 0≤m≤0.5; 0≤n≤0.5;0≤x″≤0.4; 0≤α≤1; 0≤β≤1; 0≤γ≤1; 0≤δ′≤0.4; 0≤z″≤0.4; and 0≤n′≤3; with theproviso that at least one of α, β and γ is greater than 0.

Para. J. The electrochemical cell of Para. I, wherein the cathodecomprises a cathode active material comprising LiFePO₄, LiCoO₂, LiNiO₂,LiNi_(1−x)Co_(y)M⁴ _(z)O₂, LiMn_(0.5)Ni_(0.5)O₂,LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄, LiCr_(0.5)Mn_(1.5)O₄, LiCrMnO₄,LiFe_(0.5)Mn_(1.5)O₄, LiCo_(0.5)Mn_(1.5)O₄, LiCoMnO₄, LiCoMnO₄,LiNi_(0.5)Mn_(1.5)O₄, LiNiPO₄, LiCoPO₄, LiMnPO₄, LiCoPO₄F, Li₂MnO₃,Li₅FeO₄, or Li_(x′)(Met)O₂; wherein: Met is a transition metal and1<x′≤2.

Para. K. The electrochemical cell of Para. J, wherein Met is Ni, Co, Mn,or a mixture of any two or more thereof.

Para. L. The electrochemical cell of Para. I, wherein the cathodecomprises a cathode active material comprising manganese.

Para. M. The electrochemical cell of Para. I, wherein the cathode activematerial comprises LiMn_(0.5)Ni_(0.5)O₂, LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂,LiMn₂O₄, LiM⁴ _(0.5)Mn_(1.5)O₄, Li_(1+x″)Ni_(α)Mn_(β)Co_(γ)M⁵_(δ′)O_(2−z″)F_(z″), LiMn_(0.5)Ni_(0.5)O₂, LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂,LiMn₂O₄, LiCr_(0.5)Mn_(1.5)O₄, LiCrMnO₄, LiFe_(0.5)Mn_(1.5)O₄,LiCo_(0.5)Mn_(1.5)O₄, LiCoMnO₄, LiCoMnO₄, LiNi_(0.5)Mn_(1.5)O₄, LiMnPO₄,or Li₂MnO₃; wherein: M⁴ is Al, Mg, Ti, B, Ga, Si, Mn, or Co; M⁵ is Mg,Zn, Al, Ga, B, Zr, or Ti; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu, orZn; B¹ is Ti, V, Cr, Fe, or Zr; and 0≤x≤0.3; 0≤y≤0.5; 0≤z≤0.5; 0≤m≤0.5;0≤n≤0.5; 0≤x″≤0.4; 0≤α≤1; 0≤β≤1; 0≤γ≤1; 0≤δ′≤0.4; 0≤z″≤0.4; and 0≤n′≤3.

Para. N. The electrochemical cell of any one of Paras. A-M furthercomprising a separator disposed between the cathode and the anode.

Para. O. The electrochemical cell of any one of Paras. A-N, wherein thenon-aqueous electrolyte comprises a solvent and a salt.

Para. P. A process for charging a discharged electrochemical cell, theprocess comprising: applying a voltage bias to the dischargedelectrochemical cell; and illuminating the cathode with a light source;wherein: the discharged electrochemical cell comprises a cathode, ananode, a non-aqueous electrolyte, and an illumination source.

Para. Q. The process of Para. P, wherein the light source is a broadbandwhite light source.

Para. R. The process of Para. P or Q, wherein the light source is alight emitting diode, a xenon lamp, a laser, or optical fiber.

Para. S. The process of any one of Paras. P-R, wherein the illuminationsource is a window in a housing for the electrochemical cell.

Para. T. The process of any one of Paras. P-S, wherein the illuminationsource is a fiber optic.

Para. U. The process of any one of Paras. P-T, wherein the illuminationsource further comprises an infrared filter.

Para. V. The process of any one of Paras. P-U, wherein theelectrochemical cell is a lithium ion battery, a sodium ion battery, amagnesium ion battery, or a sulfur battery.

Para. W. A method of generating Mn⁴⁺ in an electrode of anelectrochemical cell, the method comprising applying a charging currentto the electrochemical cell, and simultaneously illuminating theelectrode with visible light.

Para. X. The method of Para. W, wherein the visible light is broadbandwhite or a monochromatic light.

Para. Y. The method of Para. W or X, wherein the electrochemical cell isa lithium ion battery, a sodium ion battery, a magnesium ion battery, ora sulfur battery.

Para. Z. The method of any one of Paras. W-Y, wherein the electrode is acathode.

While certain embodiments have been illustrated and described, it shouldbe understood that changes and modifications can be made therein inaccordance with ordinary skill in the art without departing from thetechnology in its broader aspects as defined in the following claims.

The embodiments, illustratively described herein may suitably bepracticed in the absence of any element or elements, limitation orlimitations, not specifically disclosed herein. Thus, for example, theterms “comprising,” “including,” “containing,” etc. shall be readexpansively and without limitation. Additionally, the terms andexpressions employed herein have been used as terms of description andnot of limitation, and there is no intention in the use of such termsand expressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the claimed technology.Additionally, the phrase “consisting essentially of” will be understoodto include those elements specifically recited and those additionalelements that do not materially affect the basic and novelcharacteristics of the claimed technology. The phrase “consisting of”excludes any element not specified.

The present disclosure is not to be limited in terms of the particularembodiments described in this application. Many modifications andvariations can be made without departing from its spirit and scope, aswill be apparent to those skilled in the art. Functionally equivalentmethods and compositions within the scope of the disclosure, in additionto those enumerated herein, will be apparent to those skilled in the artfrom the foregoing descriptions. Such modifications and variations areintended to fall within the scope of the appended claims. The presentdisclosure is to be limited only by the terms of the appended claims,along with the full scope of equivalents to which such claims areentitled. It is to be understood that this disclosure is not limited toparticular methods, reagents, compounds compositions or biologicalsystems, which can of course vary. It is also to be understood that theterminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting.

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, particularly in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” “greater than,” “less than,” and the like,include the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember.

All publications, patent applications, issued patents, and otherdocuments referred to in this specification are herein incorporated byreference as if each individual publication, patent application, issuedpatent, or other document was specifically and individually indicated tobe incorporated by reference in its entirety. Definitions that arecontained in text incorporated by reference are excluded to the extentthat they contradict definitions in this disclosure.

Other embodiments are set forth in the following claims.

1-14. (canceled)
 15. A method of generating Mn⁴⁺ in an electrode of anelectrochemical cell, the method comprising applying a charging currentto the electrochemical cell, and simultaneously illuminating theelectrode with visible light; wherein the electrode comprises an activematerial comprising manganese.
 16. The method of claim 15, wherein theelectrode is a cathode.
 17. The method of claim 15, wherein applying thecharging current to the electrochemical cell and simultaneouslyilluminating the electrode with visible light generates Mn⁴⁺ in theelectrode at a faster rate than the same electrochemical cell in theabsence of illumination.
 18. The method of claim 16, wherein the cathodecomprises LiMn_(0.5)Ni_(0.5)O₂, LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄,LiFeO₂, LiM⁴ _(0.5)Mn_(1.5)O₄, or Li_(1+x″)Ni_(α)Mn_(β)Co_(γ)M⁵_(δ′)O_(2−z″)F_(z″); wherein: M⁴ is Al, Mg, Ti, B, Ga, Si, Mn, or Co; M⁵is Mg, Zn, Al, Ga, B, Zr, or Ti; 0≤x″≤0.4; 0≤α≤1; 0≤β≤1; 0≤γ≤1;0≤δ′≤0.4; and 0≤z″≤0.4; with the proviso that at least one of α, β and γis greater than
 0. 19. The method of claim 17, wherein the cathodecomprises LiMn_(0.5)Ni_(0.5)O₂, LiMn_(1/3)Co_(1/3)Ni_(1/3)O₂, LiMn₂O₄,LiCr_(0.5)Mn_(1.5)O₄, LiCrMnO₄, LiFe_(0.5)Mn_(1.5)O₄, LiCoMnO₄,LiNi_(0.5)Mn_(1.5)O₄, LiMnPO₄, or Li₂MnO₃.
 20. The method of claim 15,wherein illuminating the electrode comprises illuminating the electrodewith an externally powered light source.
 21. The method of claim 20,wherein the externally powered light source is a broadband white lightsource.
 22. The method of claim 20, wherein the externally powered lightsource is a monochromatic light source.
 23. The method of claim 20,wherein the externally powered light source is a light emitting diode, axenon lamp, a laser, or optical fiber.
 24. The method of claim 23,wherein the externally powered light source is a light emitting diode.25. The method of claim 15, wherein the electrochemical cell is alithium ion battery, a sodium ion battery, or a magnesium ion battery.26. The method of claim 15, wherein generating Mn⁴⁺ in the electrodecomprises oxidizing Mn³⁺ to Mn⁴⁺ in the electrode.
 27. The method ofclaim 26, further comprising, while generating Mn⁴⁺, ejecting a cationfrom the electrode.
 28. The method of claim 26, further comprising,while generating Mn⁴⁺, ejecting Li⁺ from the electrode.
 29. A method ofgenerating Mn⁴⁺ in an electrode of an electrochemical cell, the methodcomprising applying an external voltage bias to the electrochemicalcell, and simultaneously illuminating the electrode with visible light;wherein applying the external voltage bias to the electrochemical celland simultaneously illuminating the electrode with visible lightgenerates Mn⁴⁺ in the electrode at a faster rate than the sameelectrochemical cell in the absence of illumination.